1. Field of the Invention
The present invention relates to a Compact Peripheral Component Interconnect (xe2x80x9cCPCIxe2x80x9d) computer system. More specifically, the present invention relates to a bus rack for accommodating a plurality of stand-alone computers.
2. Description of Related Art
Compact Peripheral Component Interconnect (xe2x80x9cCPCIxe2x80x9d) is a high performance industrial bus based on the standard PCI electrical specification in rugged 3U or 6U Eurocard packaging. CPCI is intended for application in telecommunications, computer telephony, real-time machine control, industrial automation, real-time data acquisition, instrumentation, military systems or any other application requiring high speed computing, modular and robust packaging design, and long term manufacturer support. Because of its extremely high speed and bandwidth, the CPCI bus is particularly well suited for many high-speed data communication applications such as servers, routers, converters, and switches.
Compared to standard desktop PCI, CPCI supports twice as many PCI slots (8 versus 4) and offers a packaging scheme that is much better suited for use in industrial applications. Conventional CPCI cards are designed for front loading and removal from a card cage. The cards are firmly held in position by their connector, card guides on both sides, and a faceplate that solidly screws into the card cage. Cards are mounted vertically allowing for natural or forced convection for cooling. Also, the pin-and-socket connector of the CPCI card is significantly more reliable and has better shock and vibration characteristics than the card edge connector of the standard PCI cards.
Conventional CPCI defines a backplane environment that is limited to eight slots. One slot, the system slot, provides the clocking, arbitration, configuration, and interrupt processing for the other seven slots. Accordingly, the conventional CPCI system is limited to only one stand-alone computer since only the system slot is adapted to receive a CPU daughter card, and the other peripheral slots are reserved for peripheral daughter cards. However, many applications require larger systems so that it would be advantageous to provide multiple stand-alone computers in a CPCI system.
The present invention provides a computer bus rack that is able to accommodate a plurality of stand-alone computers, which are comprised of CPU cards that are inserted into the slots of the bus rack. The inserted CPU cards operate independently with respect to one another so that there is independent operation of the stand-alone computers. By allowing for the independent operation of multiple stand-alone computers, the present invention is able to provide the advantages of, for example, pure multitasking, parallel processing, redundancy, mirroring, back-up, and more computing power for a given board size.
The computer bus rack includes a circuit board, which is called a midplane in the present invention. The circuit board is referred to as a backplane or midplane depending on its placement in the computer chassis, which is significant. For example, if the circuit board is located at the back of the chassis so that it is a backplane, then it will allow the insertion of xe2x80x9cadd-onxe2x80x9d cards only from the front side, whereas a circuit board that is located at the middle of the chassis allows for the insertion of add-on cards from both sides--front and back. In the present invention, the circuit board is referred to as the midplane, while the conventional circuit board is referred to as the backplane.
In an embodiment of the invention, a computer bus rack has a circuit board for accommodating a plurality of stand-alone computers. The circuit board has a front side and a back side, and the rack comprises a first plurality of slots coupled to the front side, and a second plurality of slots coupled to said back side. The first and second of slots are arranged such that corresponding ones of the first and second slots are in alignment together so as to be back to back. Also, a plurality of connectors are affixed to the circuit board in alignment with the first and second plurality of slots, and have respective pass-through connector-pins that extend into each of the first and second slots, wherein certain ones of the connector-pins allocated to carry power signals are commonly connected for each of the plurality of connectors, and remaining ones of the connector-pins with respect to a particular slot are electrically isolated from connector-pins with respect to another slot on the same one of the front side and the back side.
In another embodiment of the invention, a computer system has a plurality of stand-alone computers coupled to a common circuit board, with the circuit board having a front side and a back side. The front and back sides have a plurality of slots including a plurality of connectors, with the computer system comprising a plurality of CPU daughter cards pluggable in the slots of the front side and corresponding I/O transition cards pluggable in the slots of the back side. Power signals are shared by each of the plurality of connectors of each slot, and I/O signals are only transmitted between the daughter cards on the front side and the corresponding I/O transition card on the back side.
Because the connector-pins of the slots in the midplane are not electrically connected to one another, except for the power signals, each is an xe2x80x9cisolatedxe2x80x9d bus. For example, for a given slot, only certain connector-pins transmit I/O signals, and the other connector-pins carry power signals. The connector-pins that transmit I/O signals are isolated electrically from the connector-pins of the other slots of the circuit board, whereas the connector-pins that transmit power signals are electrically connected to the connector-pins of the other slots. Thus, when a CPU card is inserted in a slot of the midplane, the I/O signals are only transmitted between the CPU card and the I/O transition card that is inserted in the corresponding slot that is on the other side of the midplane, whereas the power signals are shared with all the other slots. This allows multiple CPU cards to be inserted in the slots of the same midplane, yet operate independently. Thus, a plurality of stand-alone computers can be provided in a single midplane of the present invention. Accordingly, the midplane is able to accommodate stand-alone computers that may be used independently so as to realize the advantages of, for example, pure multitasking, parallel processing, redundancy, mirroring, back-up, or more computing power for a given board size.
A more complete understanding of the present invention will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiments. Reference will be made to the appended sheets of drawings, which will first be described briefly.